The present invention concerns a container for measuring antibodies or antigens in a biological liquid by creating specific antibody-antigen complexes, in which one element of the complex is initially associated with suspended magnetic particles that are subsequently regrouped against a certain area of one wall of the container when the container is positioned within a magnetic field that extends through that area of the wall.
In a known method of adding antibodies or antigens to a biological liquid, liquid magnetic particles associated with either antigens or antibodies specific to the respective antibodies or antigens that are to be ascertained are added to the liquid in sufficient excess to ensure that all the antibodies or antigens to be measured will combine with a respective antigen or antibody specific to them. The magnetic particles are then attracted to one wall of the container and all substances except the magnetic particles associated with their specific antigen or antibody reactant combined or uncombined with their respective antibody or antigen partner are evacuated from the container. The container is then rinsed out and a reaction liquid is introduced to create an enzymatic reaction with the antibodies or antigens. The particles are suspended in the liquid for a prescribed period and an agent is added to the liquid to terminate the reaction. Finally, magnetic particles are again attracted to the one wall of the container and the reaction liquid is measured colorimetrically.
Attracting the magnetic particles to the bottom of a dish and evacuating the biological liquid by turning the dish upside down along with the magnet, which would then maintain the particles against the bottom, has already been proposed. This procedure, however, is not very practical. Turning a dish upside down inside automatic analysis equipment necessitates a large number of mechanisms. It is also necessary to make provisions for collecting the liquid that spills out of the dishes.
One variation of the proposed method involves positioning the magnet at one side of the dish to attract the magnetic particles to a certain area of the wall. The bottom of the dish takes the form of a spherical cap which is tangent to a tubular body in the case of a dish with a circular cross-section or by a cavity with a straight generatrix which is parallel to two opposing faces of the tubular body and tangent to the faces in the case of a dish with a rectangular cross-section. The bottom walls that are tangent to the tubular section of the dish are intended to promote stirring of the liquid and to prevent dead zones which remain stationary during agitation thereby making the mixture non-homogeneous. The drawback to a dish bottom of this particular shape is that the magnet that attracts the magnetic particles to a certain area of the wall has to be constantly retained at that area in order to maintain them against the wall. This makes it necessary to provide one magnet for each dish as well as means for shifting the magnet between an active and an inactive position. When the magnet is part of automatic analysis equipment in which the dishes are transported from one operating point to another by a conveyor, it must be part of the conveyor. Such a solution is complicated and hence expensive. If the magnets are positioned only along the sections of the path of the conveyor within which the magnetic particles are to be attracted to the particular portion of the wall of the dish, the particles will slide farther along the wall every time the conveyor shifts the dish from one magnet to the next and will eventually arrive more or less at the bottom of the dish. Inasmuch as the whole method of collecting the magnetic particles within a certain area of the wall of the dish is intended to allow evacuation of the liquid with a pipette, some of the particles that slide down to the bottom will also be evacuated and will inadmissibly contaminate the measurement results.